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Optimize TLB flush in kvm_mmu_slot_remove_write_access. 

No TLB flush is needed when there's no valid rmap in memory slot.

Signed-off-by: Kai Huang <kai.huang@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Kai Huang 2015-01-12 15:28:54 +08:00 committed by Paolo Bonzini
parent 0c55d6d931
commit d91ffee9ec
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kvm/mmu.c
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@ -4302,6 +4302,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
struct kvm_memory_slot *memslot; struct kvm_memory_slot *memslot;
gfn_t last_gfn; gfn_t last_gfn;
int i; int i;
bool flush = false;
memslot = id_to_memslot(kvm->memslots, slot); memslot = id_to_memslot(kvm->memslots, slot);
last_gfn = memslot->base_gfn + memslot->npages - 1; last_gfn = memslot->base_gfn + memslot->npages - 1;
@ -4318,7 +4319,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
for (index = 0; index <= last_index; ++index, ++rmapp) { for (index = 0; index <= last_index; ++index, ++rmapp) {
if (*rmapp) if (*rmapp)
__rmap_write_protect(kvm, rmapp, false); flush |= __rmap_write_protect(kvm, rmapp,
false);
if (need_resched() || spin_needbreak(&kvm->mmu_lock)) if (need_resched() || spin_needbreak(&kvm->mmu_lock))
cond_resched_lock(&kvm->mmu_lock); cond_resched_lock(&kvm->mmu_lock);
@ -4345,7 +4347,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
* instead of PT_WRITABLE_MASK, that means it does not depend * instead of PT_WRITABLE_MASK, that means it does not depend
* on PT_WRITABLE_MASK anymore. * on PT_WRITABLE_MASK anymore.
*/ */
kvm_flush_remote_tlbs(kvm); if (flush)
kvm_flush_remote_tlbs(kvm);
} }
#define BATCH_ZAP_PAGES 10 #define BATCH_ZAP_PAGES 10